Hydrogen fluoride alkylation with effluent refrigeration

ABSTRACT

Improved processes of alkylation of isoparaffinic hydrocarbons by olefinic hydrocarbons wherein hydrogen fluoride is the alkylation reaction catalyst; processes of hydrocarbon phase effluent (alkylate, excess isoparaffinic hydrocarbons and normal paraffinic hydrocarbons) refrigeration applied to the alkylation of isoparaffinic hydrocarbons by olefinic hydrocarbons wherein hydrogen fluoride is the alkylation reaction catalyst; such improved processes of effluent refrigeration in HF catalyzed alkylation applied to systems where the reaction vessel is an elongate vertical tube interconnecting an overhead settler vessel and a below situated acid cooler vessel or a simple tank with a separate settler; processes of hydrocarbon phase effluent (alkylate, excess isoparaffinic hydrocarbons and normal paraffinic hydrocarbons) refrigeration applied to the alkylation of isoparaffinic hydrocarbons by olefinic hydrocarbons using HF catalyst wherein the alkylation reaction step, as well as the input feeds thereto are cooled by the said effluent refrigeration.

United States Patent 1191 1111 3,925,501 Putney et al. 51 Dec. 9, 1975HYDROGEN FLUORIDE ALKYLATION [57] ABSTRACT WITH EFFLUENT REFRIGERATION 5[mental-S; David pumey, shuwnefi Miss-Km Improved processes ofalkylation of isoparaffinic hy- Kansv; w A Graham, Kansas drocarbons byolefinic hydrocarbons wherem hydro- City, MO gen fluoride is thealkylation reaction catalyst; pro- 1 S a d E C t cesses of hydrocarbonphase effluent (alkylate, excess lgnee' or ngmcenng ("pom mntisoparaffinic hydrocarbons and normal paraffimc hy- Kansas Cltydrocarbons) refrigeration applied to the alkylation of 221 u Man 4 9isoparafflnic hydrocarbons by olefinic hydrocarbons wherein hydrogenfluoride is the alkylation reaction [2H Appl' 447548 catalyst; suchimproved processes of effluent refrigeration in HF catalyzed alkylationapplied to systems [52] U S (1L 2 1 3 0 34 F where the reaction vesselis an elongate vertical tube [51} Im- -z H (:07C 354 interconnecting anoverhead settler vessel and a below w f Search gay 6334 F situated acidcooler vessel or a simple tank with a separate settler; processes ofhydrocarbon phase effluent 5 References Cited (alkylate, excessisoparafiinic hydrocarbons and nor- UNITED STATES PATENTS mal paraffinichydrocarbons) refrigeration applied to the alkylation of isoparaffinichydrocarbons by ole- 'l s zflfgi z finic hydrocarbons using HF catalystwherein the alky- 29773q7 p 52 5 lation reaction step, as well as theinput feeds thereto 312131157 10/1965 Hays 11'.1.111 .1 1: 2661625148are cooled by the smd fifflua 3,233,007 2/1966 Chapman v i v aEGO/683.48 Primary Examiner-I)elbert E. Gantz 13 Clalms 3 Drawmg FiguresAssistant [imminen- Attorney, Agent. or Firm- PRESSURE CONTROL JKLVEPROPYLENE I5 BUTYLENE mums iSOBUTANE MAKE UP 10 G. J. Crasanalcis ThomasM. Scofield, Esq.

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*3 WWW HON HYDROGEN F LUORIDE ALKYLATION WITH EFFLUENT REFRIGERATIONBRIEF SUMMARY OF THE INVENTION Two U.S. Patents to David H. Putneydisclose processes for alkylation of isoparaffinic hydrocarbons byolefinic hydrocarbons utilizing effluent refrigeration. These are U.S.Pat. No. 2,664,452 Dec. 29, 1953 for Process for Alkylation UtilizingEvaporative Cooling" and U.S. Pat. No. 2,949,494, issued Aug. 16, 1960for Alkylation of Hydrocarbons Utilizing Evaporativc Cooling. These twopatents disclose effluent refrigeration for acid catalyzed alkylationwherein the reaction vessel or vessel wherein the alkylation reaction iscarried out is a circulating mixing reactor of the Stratco contactortype. Such reactors are seen in the U.S. Patent to Putney U.S. Pat. No.2,800,307, issued July 23, 1957 for Apparatus for ControllingTemperature Change of Blends of Fluids or Fluids in Finely DividedSolids". Further, the U.S. Patent to Putney U.S. pat. No. 2,977,397,issued Mar. 28, l96l, for Hydrogen Fluoride Alkylation with EffluentRefrigeration" discloses hydrogen fluoride catalyzed alkylation carriedout in such a Stratford contactor type mixing and reac tion vessel.

The present invention relates to the application of effluentrefrigeration to the cooling of alkylation reactions and the feeds (bothinitial and recycle) thereto wherein the reaction vessel is either: (a)a vertical tube connecting the underside of an overhead settler vesselto the upper portion of a below situated acid cooler or (b) a simplereaction vessel or tank with separate settler vessel. In the herebelowdescribed processes, not only is the efficient effluent refrigeration ofthe alkylation reaction carried out in these types of vessels, togetherwith the effluent refrigeration of the feed streams (both initial andrecycle) thereto, but also efficient separations of alkylate product,excess isobutane, hydrogen fluoride catalyst and normal propane orparaffinic hydrocarbons are achieved. Suitable recycles are provided, aswell as discharges from the system, thus to efficiently carry out theeffluent refrigerated HF catalyzed alkylation reactions in thesesystems.

OBJECTS OF THE INVENTION An object of the instant invention is toprovide improved hydrogen fluoride catalyzed alkylation processeswherein the alkylation reaction is carried out in vessels (or a vessel)without internal mixing, yet wherein the benefits of hydrocarbon phaseeffluent refrigeration are essentially fully achievable.

Another object of the invention is to provide improvements in alkylationprocesses utilizing hydrogen fluoride as a catalyst, the alkylationreaction being carried out in a reaction vessel of the type having anintegral settler and an integral acid cooler associated therewith, theimprovements deriving from hydrocarbon phase effluent refrigeration.

Another object of the invention is to provide improved means, method andapparatus for cooling hy drogen fluoride catalyzed alkylation reactionsby hydrocarbon phase effluent refrigeration, the hydrocarbon phaseeffluent also employed to pre-cool the feed streams to the alkylationreaction vessels.

Another object of the invention is to provide methods of and means forobtaining the evaporative cooling benefits disclosed in the US. Patentto David H. Put- 2 ney, US, Pat. No. 2,949,494, issued Aug. l6, 1960 for"Alkylation of Hydrocarbons Utilizing Evaporative Cooling" foralkylation processes which are catalyzed by hydrogen fluoride andadditionally have little or no alkylation reaction vessel internalmixing and circulation.

Another object of the invention is to provide methods of and means forefficiently separating (for recycle) the hydrogen fluoride catalyst ofan alkylation reaction from the hydrocarbon phase effluent from thesettler in an alkylation system where the hydrocarbon phase effluent isemployed in eflluent refrigeration both of the alkylation reaction stepin the vessel and feed streams thereto.

Another object of the invention is to improve alkylation reactionprocesses catalyzed by hydrogen fluoride wherein the alkylation reactorcomprises a tubular con duit between an overhead settler vessel and abelow situated acid cooler vessel, the improvements comprising passingthe hydrocarbon phase effluent from the settler through a pressurereducing valve, thereby to chill same by self-evaporative cooling,thereafter passing the effluent through cooling elements in the acidcooler vessel, whereby to remove heat from and aid in controlling thetemperature of reactants in the tubular reactor.

Another object is to improve such described processes by passing thechilled hydrocarbon phase effluent, after use as a refrigerant in theacid cooler vessel and, optionally, as a refrigerant with the incomingfeeds to the tubular reactor, to a separating phase or stage where anyentrained hydrogen fluoride is taken off overhead as vapors (withpropane) same passed to a depropanizer and Hf stripper step, one portionof the liquid bottoms from the separating step comprising isobutane andalkylate passed to a deisobutanizer and a second liquid bottoms portioncomprising isobutane passed in recycle to the feeds to the alkylationreactor.

Another object of the invention is to provide improved means of andmethods for hydrogen fluoride catalyzed alkylation in systems whereinthe alkylation reactor has no internal circulation means and there is aseparate settling vessel, the hydrocarbon phase effluent overhead fromthe settler being passed through a pressure reducing valve where it ischilled by a selfevaporative cooling, the chilled, pressure-reducedhydrocarbon phase effluent, both liquid and vapor phases, then beingpassed through cooling elements in the alkylation reaction vessel toremove heat from and control the temperature of the reactant mixture, aswell as being passed in indirect heat exhange with the feed ele ments tothe reactor, the acid bottoms from the settler being recycled to thenon-circulating reactor as catalyst and optionally being passed inindirect heat exchange with at least a portion of the chilled,pressure-reduced hydrocarbon phase effluent.

Another object of the invention is to provide such described processwherein the chilled, pressure reduced hydrocarbon phase effluent, afteruse as refrigerant in the alkylation reactor and with the recycle acidphase and hydrocarbon feeds to the reactor, is then passed to avapor-liquid separating step where compressed vapor, including somehydrogen fluoride, is passed to depropanizing and HF stripping steps forrecycle of the hydrogen fluoride to the feed to the reactor, the liquidbottoms from the vapor-liquid separating stage comprising a first part,including alkylate, sent to a deisobutanizer and a second part, largelycomprising isobutane which is recycled to the feed to the reactor.

It is well known that there are distinct process advantages obtainableby operating a hydrogen fluoride alkylation plant at temperatures lowerthan obtainable with water cooling of the reactor. These benefitsinclude increased octane number and yield of the resulting alkylate.This invention makes that possible since the HF alkylation units builtin the past and now being built are water cooled.

Other and further objects of the invention will appear in the course ofthe following description thereof.

The three drawings comprise schematic flow diagrams of embodiments ofthe invention.

FIG. 1 is a schematic flow diagram of one embodiment of the improvedhydrogen fluoride catalyzed alkylation process, the alkylation reactorcomprising a vertical tube communicating between an overhead settlervessel and a below located acid cooler vessel, effluent refrigerationbeing applied to the feeds to the tubular reactor and the acid cooler.

FIG. 2 is a schemattic flow diagram of a second embodiment of theimproved hydrogen fluoride catalyzed alkylation process, the alkylationreaction vessel, settler and acid cooler being of the same type as thatseen in FIG. 1, the process differing in the handling of the recyclehydrogen fluoride from the HF stripper and the regenerator, as well asthe disposition of the hydrocarbon phase effluent after same is used aseffluent refrigerant in the acid cooler and the hydrocarbon feeds to thealkylation reactor.

FIGv 3 is a schematic flow diagram of a modified form of the improvedhydrogen fluoride catalyzed alky lation process, the alkylation reactorcomprising a simple vessel without internal circulation or mixing means,there being a separate settler vessel, the hydrocarbon phase effluentfrom the settler being used as effluent refrigerant to l the alkylationreactor, (2) the recycle acid from the settler and (3) the hydrocarbonfeed to the reactor vessel.

FIG. I HG CATALYZED ALKYLATION EFFLUENT REFRIGERATION TUBULAR REACTORVV'ITH OVERHEAD SETTLER AND BELOW LOCATED ACID COOLER Referring first toFIG. 1, therein is shown an alkylation system wherein isoparaffmichydrocarbons are alkylated by olefinic hydrocarbons in the presence ofhydrogen fluoride as a reaction catalyst. In this system, effluentrefrigeration is employed. The reaction vessel comprises an elongatevertical tube interconnecting an overhead settler vessel and a belowsituated acid cooler vessel. there being an additional, valve controlledrecycle flow line interconnecting the settler and acid cooler, wherebycirculation of liquids occurs upwardly from the acid cooler to thesettler in the reaction vessel and vice versa in the flow line(clockwise in this view of FIG. 1 by gravity flow because of thedifference in specific gravity of the liquids in the two vertical tubes.

At there is seen the tubular reactor connecting and communicating at itsupper end with a settler vessel II and connecting and communicating atits lower end with an acid cooler 12. A valve controlled second verticaltube 13 communicates between and connects settler I1 and acid cooler 12,the control valve indicated at 14. Tubes 10 and I3 connect the upperside of the acid cooler 12 with the underside of settler 1].

Sensor 15 measures the entering temperature of liquids circulatingupwardly in tubular reactor 10, while sensor 16 measures the leavingtemperature of such liq uids adjacent the upper end of the tubularreactor. These sensors are coupled with a temperature differ encecontrol 17 which operates or throttles valve 14. Briefly stated, thegreater the temperature differential between sensors 15 and 16, the morevalve 14 is open. whereby to increase the circulation and obtain morecooling of the alkylating reactants in the tubular reactor.

Looking at the lower left-hand corner of FIG. 1, input flow lines l820,inclusive for propylene, butylene, amylene and isobutane make-up,respectively,join in common line 21. The contents of line 21, afterjoinder thereto of isobutane recycle line 51 (to be described) arecooled in indirect heat exchanger at 22, passing to input feed lines 23which have input venturis or nozzles 24 and 25, respectively, at theends thereof positioned at the inlet 10a of tubular reactor 10.

Circulating in the vessel configuration of tubular reactor 10, settler11, return line 13 and acid cooler 12 are an excess of isobutane,olefinic hydrocarbons, hydrogen fluoride catalyst and alkylate. Catalystinput to this system is through line 26 fed by line 27 from the HFregeneration and stripping systems, respectively, to be described, withmake-up HF catalyst added through line 28, as required. In settler 11there is a gravity separation of HF catalyst which fails and tends toreturn to cooler 12 through line 13. The lighter hydrocarbons: alkylate,excess isoparaffmics and normal hydrocarbons rise to the top of settler11. The entire vessel system (10, ll, 12 and 13) is liquid full.

Line 29 comes off overhead from settler 11 and has back pressure controlvalve 30 thereon. Valve 30 maintains the settler, reactor and acidcooler system under sufficient back pressure so as to maintain all ofthe reactants and fluids therein in liquid phase. Withdrawn overheadthrough line 29 is the hydrocarbon phase effluent, including primarilyalkylate and isobutane with some propane and HF catalyst. After passingback pressure control valve 30, the pressure is so reduced on thehydrocarbon phase effluent as to refrigerate it and vaporize excessvolatile hydrocarbons. Any alkylate therein is non-evaporable under thepressures and temperatures existing in this system. Line 29, after backpressure valve 30, divides into lines 31 (having valve 31a thereon) and32 (having valve 320 thereon).

Some portion of the refrigerated hydrocarbon phase effluent, controlledby valves 31a and 32a, may be passed through line 3] in indirect heatexchange with the input feed components (olefins and isobutane) in line21 at heat exchanger 22. The majority (or all) of the flashedhydrocarbon phase effluent is passed through line 32 (controlled byvalves 31a and 32a) into a tube bundle 33 schematically indicated in theacid cooler I2. The return line 34 out of acid cooler 12 from tubebundle 33 is joined by line 31 after heat exchange at 22. All of thehydrocarbon phase effluent, then, after indirect heat exchange (effluentrefrigeration) of the acid cooler and, optionally, heat exchanging of(cooling) the feed inputs to the tubular reactor 10, are passed via line35 to suction trap and flash drum 36.

Suction trap and flash drum 36 is an elongate horizontal tank having avertical divider 37 thcrewithin. A first withdrawal line 38 (on the lefthand side ofthe tilvider 37 in the view of FIG. I adjacent thehydrocarbon phase effluent input from line 35 takes a first quantity ofliquid bottoms (largely comprising alkylate) from vessel 36 through pump38a in a quantity controlled by. \ulvc 39 and level control 391:. I.inc38 thereafter passes through a heat exchanger at 39b to deisobutanizervessel 40. Bottoms from deisobutanizer 40 are taken off through line 41through heat exchange at 39b, with the majority of the bottoms from thedeisobutanizer thereafter being passed from the system through line 42comprising alkylate and butane. Circulating line 43 with heat exchanger(heater) 44 is also provided for reboiling tower bottoms. The overheadfrom deisobutanizer 40 through line 45 is condensed at 46, thereafterpassing to accumulator vessel 47. Isobutane is taken from accumulator 47by line 48 through pump 49 which drives the isobutane either in recycleback to tower 40 via line 50 or to join line 21 of the feed through line51.

Returning to trap and drum 36, a second liquid bottoms line 52 is drivenby pump 53 as controlled by valve 54 and level control 54a in recyclevia line 55 to join the input olefin and isobutane feeds to the system,as well as the fractionation recycle isobutane, in line 21.

Light hydrocarbon vapors are taken overhead from vessel 36 through line56, passing through compressor 57 and condenser 58 to collection inaccumulator vessel 59. The liquefied light hydrocarbons are taken fromvessel 59 through line 60 driven by pump 61 and controlled by valve 62and level control 62a from whence line 60 splits into two lines 600 and60b. Through line 60b, a portion of the liquefied light hydrocarbonsfrom vessel 59 are recycled to the right hand cell of trapdrum 36. Agreater quantity, at least, of the lighter hydrocarbons are taken vialine 60a through heat exchange at 64 to depropanizer 65.

Line 38 contains substantially all of the alkylate product, the externalisobutane recycle in be fractionated to the deisobutanizer tower, thenormal butane which entered with the feed stocks, some propane andhydrogen fluoride. Line 52 contains propane, considerable isobutane,some hydrogen fluoride, some normal butane but very little alkylate.Line 56 contains all of the effluent recycle isobutane, some hydrogenfluoride, propane, normal butane and a very small amount of alkylate.

Bottoms from depropanizer 65 are taken off through line 66 which splitsinto two lines 67 and 68. Line 68 passes in heat exchange at 64 andthereafter is recycled, after cooling at 69, back to suction trap andflash drum 36. A reflux may be taken via line 67 back to depropanizer 65after heating at 70.

The overhead from depropanizer 65, comprising largely propane andcatalyst HF passes via line 71 through cooling at 72 to accumulation invessel 73. Bottoms from vessel 73 are taken out via line 74 driven bypump 75. The discharge from pump 75 separates into recycle line 76 backto the upper portion of the depropanizer tower and line 77 which passesto HF stripper vessel 78.

Botttoms from the HF stripper 78, comprising propane, pass out of thesystem via line 79. The HF overhead line 80 passes through a coolingstep at 81 and through pump 82. Discharge from the pump through line 83splits into. a recycle line 85 to the stripper and a recycle line 86which takes HF catalyst back to the system as will be described.

Returning to settler 11, since the system of tubular reactor 10, settlerll, recycle line 13 and acid cooler 12 is operated liquid full, there isa tendency for the heavier catalyst to fall to the bottom of settler 11,as well as a tendency for the lighter hydrocarbon phase effluent ofalkylate, excess isobutane and light hydrocarbons to rise to the top.Therefore, take off line 87 from the lower part of settler l1 spacedaway from tubular reactor 10 is provided, having valve 88 thereon. I-IFcatalyst liquid withdrawn from settler I1 is passed via heat exchangeheating at 89 to HF regenerator 90. Regenerator 90 is heated by indirectheat exchange coil 91 having input and output lines 92 and 93. Tar isremoved from the system through line 94. HF catalyst is taken offoverhead of regenerator 90 via line 95 and passed through a cooling stepat 96 to HF accumulator vessel 97. Accumulated HF catalyst is recycledto the system through line 98 which is joined by recycle line 86 fromthe HF stripper 78. As seen in FIG. 1, these lines combine at 27,thereafter joined by make up HF line 28 in feed to recycle tube 13 vialine 26.

FIG. 2 HF CATALYZED ALKYLATION IN REACT OR-SE'ITLER-ACID COOLER SYSTEMWITH EFFLUENT REFRIGERATION (SECOND FORM) FIG. 2 is a schematic flowdiagram of a process of alkylating isoparaffinic hydrocarbons witholefinic hydrocarbons in the presence of hydrogen fluoride as thealkylation reaction catalyst, the reaction vessel comprising an elongatevertical tube interconnecting an overhead settler vessel and a belowsituated acid cooler vessel. There is additionally provided a valvecontrolled recycle flow line interconnecting the settler and acidcooler, whereby circulation of liquids occurs upwardly from the acidcooler to the settler in the reaction vessel and vice versa in recycleflow. The system illustrated and described herebelow resembles that ofthe described system of FIG. 1 in numerous ways. However, it alsodiffers in numerous respects, among which are included the use of asingle section suction trap and flash drum.

Referring then to FIG. 2, a tubular vertical reactor 100 communicatesbetween the lower portion of a settler vessel 101 and the upper portionof an acid cooler vessel 102. A recycle line or column 103 is providedcommunicating between the upper part of acid cooler 102 and the lowerpart of settler 101 spaced from tubular reactor 100. Valve 104 iscontrolled with respect to recycle flow down leg or tube 103 bytemperature differential control 105. The latter is linked with enteringtemperature sensor 106 and leaving temperature sensor 107, the formerpositioned in the lower reaches of reactor 100, the latter positioned inthe upper portion thereof. Circulation in the reactionvessel-settler-acid cooler system is upwardly in reactor 100 anddownwardly in tube or pipe 103. This leads to a clockwise circulation ofliquids in the system of FIG. 2. The impetus for such flow is, first,the input of new reactants to be described moving upwardly in leg orreactor 100 and, additionally, the driving force of the increasedtemperature within the reactor 100, which tends to cause the liquidstherein to rise in the vessels system. Likewise, the higher specificgravity of the liquids in the lower portion of the settler 101 adjacenttube 103 tends to cause the liquids to fall in such leg.

Looking at the lower left-hand comer of FIG. 2, input flow lines109-111, inclusive provide propylene, butylene, amylene and isobutanemake-up, respectively, joining in common line 112. Line 112, afterreceiving a recycle isobutane line (to be described) is optionally heatexchanged (cooled) at 1 l3 and thereafter passes, after joinder by an HFcatalyst recycle line, (to

7 be described) to input feed lines 114 and 115 which pass into acidcooler 102 to discharge nozzles or venturis 116.

Circulating in the vessel configuration of tubular reactor 100, settler101, return line 103 and acid cooler 102 are an excess of isoparaffinichydrocarbons (isobutane) olefinic hydrocarbons, hydrogen fluoridecatalyst and alkylate. The primary alkylation takes place in the tubularreactor 100 between sensors 106 and 107. Catalyst input to this systemis through line 117 joining line 112 immediately before tubular reactor100 fed by line 118 from the HF regeneration and stripping systems, (tobe described) with make up HF catalyst added through line 119, asrequired. In settler 101, there is a gravity separation of HF catalystwhich falls and tends to return to cooler 102 through line 103. Thelighter hydrocarbons including alkylate, excess isoparaffins and normalhydrocarbons, rise to the top of settler 101. The entire vessel system(101, 102, 100 and 103) is liquid full.

Taken overhead from settler 101 through line 120 is the hydrocarbonphase effluent comprising alkylate, some HF, excess isoparaffinichydrocarbons and light normal paraffins. Back pressure valve 121maintains the settler, reactor and acid cooler system under sufficientback pressure so as to maintain all of the reactants and fluids thereinin liquid phase.

After passing back pressure control valve 121, the pressure is soreduced on the hydrocarbon phase effluent in line 120 as to refrigerateit and vaporize excess volatile hydrocarbons. Any alkylate therein isnon-evaporable under the pressures and temperatures existing in thesystem. Line 120, after back pressure valve 121 divides into lines 122(having valve 122a thereon) and 123 (having valve 123a thereon).

Some portion of the refrigerated hydrocarbon phase effluent, controlledby valves 122a and 123a, may be passed through line 122 in indirect heatexchange with the input feedcomponents (olefins and isobutane) in line 112 at heat exchanger 113. The majority (or all) of the flashedhydrocarbon phase effluent is passed through line 123 (controlled byvalves 122a and 123a) into a tube bundle 124 schematically indicated inthe acid cooler 102. The return line 125 out of acid cooler 102 from thetube bundle 124 is joined by line 122 after the heat exchange at 113.All of the hydrocarbon phase effluent, therein, after indirect heatexhange (effluent refrigeration) of the acid cooler and, optionally,heat exchanging of (cooling) the feed inputs to the tubular reactor 100,are passed via line 126 to suction trap and flash drum 127.

Liquid bottoms from vessel 127 are taken off line 128 through pump 129controlled by valve 130 and level control 130a, to deisobutanizer 133via line 131. Bottoms from deisobutanizer 133 are removed through line134 from which a circulating line 135 heated at 136 returns to tower133. Valve 137, operated by level control 1370, controls the flow inline 134 which passes through heat exchange (optionally) at 132 andagain at 138. Thereafter, line 134 departs from the system carryingalkylate product after optional cooling at 139.

Deisobutanizer overheads through line 140 condense at 141 and accumulatein vessel 142. Liquid isobutane is then recycled via line 143 throughpump 144 partly back to the top of deisobutanizer 133 through line 145as required for reflux with the balance to the feed inputs to tubularreactor 100 through line 146 which joins the feed line 112 before heatexchange at 113.

Returning to suction trap 127, the overhead vapors from vessel 127 aretaken off through line 147, compressed at 148, condensed at 149 andaccumulated in vessel 150. These condensed vapors, including HF catalystand largely paraffinic hydrocarbons, particularly isobutane with somepropane, are taken off through bottoms line 151 driven by pump 152 andcontrolled by valve 153 and level control 153a. After valve 153,1ine 151splits into lines 154 and 155. The former, after joined by a line to bedescribed, passes as line 156 to join the feed input line 112,comprising the isobutane effluent refrigeration recycle. Line 155, afterheat exchange at 138 (optional) passes to depropanizer 157.

Bottoms from depropanizer 157 are taken off through line 158 controlledby valve 159 and level control 1590. Before valve 159, circulation line160 may be provided with heater 161. Thereafter the depropanizer bottomspass via line 162 through a cooling step at 163 to join line 154 as partof the isobutane effluent refrigeration recycle in line 156.

Overheads from depropanizer 157 pass out line 164 through condensor 165to accumulation in vessel 166. Liquid from accumulator 166 passes vialine 167 driven by pump 168 partly in recycle to the tower as reflux vialine 169 and through line 170 to HF stripper 171.

Bottoms from HF stripper 171 pass via line 172a (largely propane) out ofthe system. The overhead hydrogen fluoride catalyst from stripper 171passes via line 172 through condensor 173 to accumulation in vessel 174.The liquid from accumulator 174 passes via line 175 through pump 176either in recycle via line 177 to the HF stripper 171 or as HF catalystrecycle via line 178 joining a line from the HF regenerator (to bedescribed) becoming common line 118 already noted.

Returning to settler 101, as previously noted, there is a verticalseparation of the catalyst (settles lower) and the hydrocarbon phaseeffluent (rises higher) in settler 101. Bottoms from settler 101 arepassed via line 179 controlled by valve 180 to HF regenerator 181.Regenerator vessel 181 is heated via coil 182 with heating fluid inputand output lines 183 and 184. Tar is passed out of the system from theregenerator via line 185. Overhead from vessel 181, hydrogen fluoridecatalyst is passed via line 186 through condensation at 187(accumulation), the liquid HF thereafter going via line 188 through pump1B9 either in recycle to the regenerator through line 190 or back to thesystem in line 191 which joins stripper return line 178 thereafterbecoming recycle line 118.

FIG. 3 HYDROGEN FLUORIDE CATALYZED ALKYLATION IN NON-CIRCULATING REACTORWl lI-l SEPARATE SE'ITLER Turning to FIG. 3, at 200 there is seen thereaction vessel which comprises a simple tank with little or no internalmixing or, at least, no circulated mixing utilizing a circulation tubeas in the case of a Stratford contactor (US. Pat. No. 2,979,308 toPutney, issued Apr. 1 l, 1961 for Apparatus for Controlling TemperatureChange and US. Pat. No. 2,800,307 to Putney issued July 23, 1957 forApparatus for Controlling Temperature Change There is a separatesettling vessel 201.

Referring to the lower left hand corner of FIG. 3, propylene, butyleneand amylene (olefinic hydrocarbons) in separate or individual streams202-204, inclusive, as well as isobutane make-up through line 205, joinin common line 206 which is passed in indirect heat exchangingrelationship (cooling of these streams) at 207. Line 206 thereafterpasses to reactor 200 furnishing the basic olefinic and isobutanemake-up feeds thereto, as well as other streams which have joined thisline (which will be described herebelow In the reactor 200,isoparaffinic hydrocarbons, particularly isobutane, are alkylated byolefinic hydrocarbons (propylene, butylene and amylene) in the presenceof hydrogen flouride as a reaction catalyst.

A mixture of HF catalyst, alkylate, excess isobutane and lightparaffinic hydrocarbons such as propane are discharged via line 208 tosettler 201. In settler 201, there is a gravity separation of thehydrogen fluoride catalyst (falls downwardly in the settler) and ahydrocarbon phase consisting of alkylate, isobutane and light paraffinichydrocarbons. A first catalyst recycle line 209 from the underside ofsettler 201 passes to pump 210 carrying recycle HF catalyst which goesinto indirect heat exchange (cooling of the catalyst) at heat exchanger207, thereafter being recycled as catalyst feed to the reactor 200.Make-up HF line 2090 may join line 209 as shown to provide additionalcatalyst as may be required by the system.

A second catalyst withdrawal line 211 with flow therethrough controlledby valve 212 passes to HF regenerator 213. Tar bottoms from theregenerator are passed out of the system through line 214. A heatingcoil 215 is provided in the regenerator fed by input and output lines216 and 217. The overhead discharge of catalyst from regenerator 213 isthrough line 218 to condensation at 219 and passage to pump 220. Frompump 220, a quantity of the catalyst is recycled to the regeneratorthrough line 221, the balance returned to the system through line 222.

Turning back to settler 201, taken off overhead through line 223 is theentire hydrocarbon phase effluent comprising alkylate, excess isobutane,light paraffinic hydrocarbons and a small quantity of HF catalyst. Backpressure valve 224 maintains settler 201 and reactor 200 undersufficient back pressure to maintain all the reactants and fluidtherewithin in liquid phase. In passing valve 224, the pressure isreduced on the hydrocarbon phase effluent whereby to refrigerate it andvaporize excess volatile hydrocarbons. The alkylate is non-evaporableunder the pressures and temperatures existing in the system.

Flow line 225 having control valve 226 thereon passes to a heatexchanging coil or tube bundle 227 in reactor 200, the return line 228passing to suction trap and flash drum 229. Line 223, after the take offfor line 225, is numbered 230 with valve 231 thereon and passes to heatexchanger 207, the return line therefrom, 232, joining line 228 beforeit reaches suction trap and flash drum 229.

The reduced temperature, flashed hydrocarbon phase effluent, both liquidand vapor, in combination, may be passed in its entirety or just aportion thereof through line 225, controlled by valves 226 and 231,whereby to cool the alkylation reaction zone in reactor 200.Alternatively, all or a portion of the reduced temperature, flashed,hydrocarbon phase effluent, again controlled by valves 226 and 231, maypass through line 230 in indirect heat exchanging relationship withlines 209 and 206, whereby to cool the recycle catalyst feed to thereactor and the input hydrocarbon phase feed to the reactor. Generallyspeaking, the greatest proportion of the refrigerated hydrocarbon phaseeffluent will be passed in indirect heat exchange with the al- 10kylation reaction itself in tube bundle or coil 227 in vessel 200.

At any rate, all of the flashed, refrigerated hydrocarbon phaseeffluent, both liquid and vapor in combination, is passed via line 228to suction trap and flash drum 229.

Line 234 to deisobutanizer 236 via pump 235 contains substantially allof the alkylate product, the external isobutane recycle in befractionated to the deisobutanizer tower, the normal butane whichentered with the feed stocks, some propane and hydrogen fluoride. Line244 contains propane, considerable isobutane, some hydrogen flouride,some normal butane but very little alkylate. Line 246 contains all ofthe effluent recycle isobutane, some hydrogen fluoride, propane, normalbutane and a very small amount of alkylate.

Bottoms from deisobutanizer 236 are taken off through line 238controlled by valve 239 and level control 239a. Circulating line 240 istaken off line 238 and back to the deisobutanizer through heater 241.The contents of line 238 are passed in indirect heat exchange at 237 andthereafter (optionally) at 242 with the feed to the depropanizer (to bedescribed), thereafter passing from the system as alkylate product aftercooling at 243.

Returning to trap 229, bottoms from the right hand cell (in the view ofFIG. 3) are taken off through line 244 driven by pump 244a. After pump2440, line 244 has control valve 245 thereon controlled by level control245a. Line 244 carries isobutane in recycle to join main feed line 206leading to reactor 200.

Vapor overheads (light hydrocarbons with some catalyst contamination)from trap 229 are taken off through line 246, compressed at 247,condensed at 248 and accumulated in vessel 249. The accumulated liquidsin vessel 249 are discharged through line 250 driven by pump 251 andcontrolled by valve 252 and level control 252a. The contents of line 250are passed in indirect heat exchange at 242 with the alkylate prod uetand thereafter go to depropanizer 253. Recycle line 254 taken off fromline 250 after valve 252 returns some of the compressed, condensedoverhead from line 246 to right hand cell of trap-drum 229.

Depropanizer bottoms are discharged through line 255 controlled by valve256 and level control 256a. After cooling at 257, line 255 joins line254 for recycle to the main feed to the reactor 200. Circulating line258 may be taken off line 255 with heating at 259.

The overhead from depropanizer 253 is withdrawn through line 260 withcondensation at 261 and accumulation at vessel 262. Bottoms fromaccumulator 262 are taken off through line 263 driven by pump 264 withthis liquid either recycled to depropanizer 253 through line 265 asreflux to the depropanizer or passed via line 266 to HP stripper 267 (orboth).

The bottoms from stripper 267, comprising largely propane, are withdrawnfrom the system at 268. The overhead line 269 from stripper 267,carrying hydrogen fluoride catalyst, is condensed at 270, andaccumulated at vessel 271. The accumulated catalyst in vessel 271 ispartly recycled to stripper 267 via line 272 and balance is passed backto the basic feed input to reactor 200 via line 273, by pump 274.

From the foregoing, it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the process.

It will be understood that certain process features, steps andsub-combinations thereof are of utility and may be employed withoutreference to other features, steps and process subcombinations. This iscontemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

We claim:

1. A process of effluent refrigeration applied to the alkylation ofisoparaffinic hydrocarbons by olefmic hyrodcarbons wherein hydrogenfluoride is the alkylation reaction catalyst and the reaction vesselcomprises an elongate vertical tube interconnecting an overhead settlervessel and a below-situated acid cooler vessel, there being anadditional valve-controlled recycle flow line interconnecting thesettler and acid cooler,

whereby circulation of liquid alkylation reaction mixture occursupwardly through said reaction vessel to said settler and separated acidreturns from said settler downwardly through said flow line to saidcooler vessel, comprising the steps of:

a. admixing said isoparaffinic hydrocarbons and said olefinichydrocarbons with liquid hydrogen fluoride catalyst in an alkylationreaction step in said reaction vessel,

b. passing said reaction mixture of hydrocarbons, including alkylate,propane and isobutane, and said catalyst from said reaction vesseloverhead to said settler,

c. maintaining said settler, said reactor and said acid cooler undersufficient back pressure to maintain all of said reaction mixture inliquid phase,

d. withdrawing overhead from said settler a hydrocarbon phase whichcomprises primarily isobutane and alkylate and a minor amount of propaneand catalyst,

e. reducing the pressure on said hydrocarbon phase to vaporize excessvolatile hydrocarbons, thereby refrigerating said hydrocarbon phase,

f. passing at least a substantial portion of said refrigeratedhydrocarbon phase, including both liquid and vapor without separation,in indirect heat exchange with said acid in said acid cooler whereby tolower the temperature thereof,

g. passing said hydrocarbon phase, after use of same as a heat exchangemedium in step (f) to a vapor-liquid separating step,

h. the vapor phase from said separating step being passed to adepropanizing step and overhead from said depropanizing step beingpassed to an HF stripping step,

. recycling hydrogen fluoride catalyst from said stripping step to thealkylation reaction in step j. passing a first portion of the separationstep liquid bottoms from step (g) to a deisobutanizing step andrecycling overhead liquids from said deisobutanizing step to thereaction step (a), and

k. withdrawing alkylate product bottoms from said deisobutanizing step.

2. A process as in claim 1 including passing all of the saidrefrigerated hydrocarbon phase in indirect heat exchange with the liquidacid in said acid cooler.

3. A process as in claim 1 including passing a minor portion of the saidrefrigerated hydrocarbon phase in indirect heat exchanging relationshipwith the feeds to the reaction step (a).

4. A process in claim 1 including recycling the depropanizing stepbottoms to said vapor-liquid separating step (g).

5. A process as in claim 1 including passing a second portion of theseparation step liquid bottoms from step (g) as recycle feed to thealkylation reaction step.

6. A process as in claim 1 wherein hydrogen fluoride catalyst isrecycled from the HF stripping step to said flow line from said settlerto said acid cooler.

7. A process as in claim 1 wherein hydrogen fluoride catalyst isrecycled from said HF stripping step to join the hydrocarbon reactantfeeds to the reaction step.

8. A process of effluent refrigeration applied to the alkylation ofisoparaffinic hydrocarbons by olefinic hydrocarbons wherein hydrogenfluoride is the alkylation reaction catalyst and the reaction vesselcomprises an elongate vertical tube interconnecting an overhead settlervessel and a below-situated acid cooler vessel,

there being an additional valve-controlled recycle flow lineinterconnecting the setter and acid cooler, whereby circulation ofliquid alkylation reaction mixture occurs upwardly through said reactionvessel to said settler and separated acid returns from said settlerdownwardly through said flow line to said cooler vessel, comprising thesteps of:

a. admixing said isoparaffinic hydrocarbons and said olefmichydrocarbons with liquid hydrogen fluoride catalyst in an alkylationreaction step in said reaction vessel,

b. passing said reaction mixture of hydrocarbons, including alkylate,propane and isobutane, and said catalyst from said reaction vesseloverhead to said settler,

c. maintaining said settler, said reactor and said acid cooler undersufficient back pressure to maintain all of said reaction mixture inliquid phase,

d. withdrawing overhead from said settler a hydrocarbon phase whichcomprises primarily isobutane and alkylate and a minor amount of propaneand catalyst,

e. reducing the pressure on said hydrocarbon phase to vaporize excessvolatile hydrocarbons, thereby refrigerating said hydrocarbon phase,

f. passing at least a substantial portion of said re frigeratedhydrocarbon phase, including both liquid and vapor, without separation,in indirect heat exchange with said acid in said acid cooler, whereby tolower the temperature thereof,

g. passing said hydrocarbon phase, after use of same as a heat exchangemedium in step (f) to a vapor-liquid separating step,

h. a first portion of said vapor phase from said separating step beingpassed to a depropanizing step and overhead from said depropanizing stepbeing passed to an HF stripping step,

. recycling hydrogen fluoride catalyst from said stripping step to thealkylation reaction in step j. a second portion of said vapor phaseseparated from said separating step being recycled after compression andcondensation to join the hydrocarbon reactant feeds to the reaction step(a), and

k. separating an alkylate product from the liquid bottoms from saidseparating step.

9. A process as in claim 8 wherein the liquid bottoms from saidseparating step (g) are passed in their entirety to a deisobutanizingstep, the overhead from the deisobutanizing step being recycled to thereaction step (a) and the liquid bottoms from said deisobutanizing stepbeing withdrawn as alkylate product.

10. A process of effluent refrigeration applied to the alkylation ofisoparaffinic hydrocarbons by olefinic hydrocarbons where hydrogenfluoride is the alkylation reaction catalyst, there being separatevessels for reaction and settling steps comprising;

a. admixing said isoparaffinic hydrocarbons and said olefinichydrocarbons with liquid hydrogen fluoride catalyst in an alkylationreaction step in said reaction vessel,

b. passing said reaction mixture of hydrocarbons, in-

cluding alkylate, propane and isobutane, and said catalyst from saidreaction vessel to said settler,

c. maintaining said settler and said reaction vessel under sufficientback pressure to maintain all of said reaction mixture in liquid phase,

d. separating hydrogen fluoride catalyst as liquid bottoms from saidsettling step and recycling a first portion of said catalyst to thereaction step (a),

e. withdrawing overhead from said settler a hydrocarbon phase whichcomprises primarily isobutane and alkylate and a minor amount of propaneand catalyst,

f. reducing the pressure on said hydrocarbon phase to vaporize excessvolatile hydrocarbons and thereby refrigerate said hydrocarbon phase,

g. passing at least a substantial portion of said refrigeratedhydrocarbon phase, including both liquid and vapor without separation,in indirect heat exchange with said reaction mixture in the reactionstep (a) whereby to lower the temperature thereof,

h. said refrigerated hydrocarbon phase, after being used as a heatexchange medium, being passed to a separating step wherein liquid andvapor phases are separated and a first portion of the liquid phase fromsaid separating step is passed to a deisobutanizing step,

. the overhead from said deisobutanizing step being recycled to thereaction step (a), the liquid bottoms from the deisobutanizing stepbeing withdrawn as alkylate product,

j. a second portion of said catalyst from said settling step beingpassed to a hydrogen fluoride regenerating step, and the regeneratedhydrogen fluoride catalyst from said regenerating step is recycled tothe alkylation reaction step (a),

k. the vapor phase from said separating step being compressed, condensedand passed to a depropanizing step and overhead from said depropanizingstep being passed to an HF stripping step, and

l. the propane bottoms from said stripping step being withdrawn from theprocess and hydrogen fluoride overhead from said stripping step beingrecycled to the alkylation reaction zone (a).

11. A process as in claim 10 wherein a portion of said refrigeratedhydrocarbon phase is passed in indirect heat exchanging relationshipwith a catalyst recycle from the settling step (b) to the reaction step(a).

12. A process as in claim 10 wherein a minor portion of saidrefrigerated hydrocarbon phase is passed in indirect heat exchangingrelationship with the hydrocarbon reactant feeds to the reaction step(a).

13. A process as in claim 10 wherein a minor portion of saidrefrigerated hydrocarbon phase is passed in indirect heat exchangingrelationship with both the catalyst recycle from the settling step (b)and the hydroc arbon reactant feeds to the reaction step (a).

1. A PROCESS OF EFFLUENT REFRIGERATION APPLIED TO THE ALKYLATION OFISOPARAFFINIC HYDROCARBONS BY OLEFINIC HYDROCARBONS WHEREIN HYDROGENFLUORIDE IS THE ALKYLATION REACTION CATALYST AND THE REACTION VESSELCOMPRISES AN ELONGATE VERTICAL TUBE INTERCONNECTING AN OVERHEAD SETTLERVESSEL AND A BELOWSITUTATED ACID COOLER VESSEL, THERE BEING ANADDITIONAL VALVE-CONTROLLED RECYCLE FLOW LINE INTERCONNECTING THESETTLER AND ACID COOLER WHEREBY CIRCULATION OF LIQUID ALKYLATIONREACTION MIXTURE OCCURS UPWARDLY THROUGH SAID REACTION VESSEL TO SAIDSETTLER AND SEPARATED ACID RETURNS FROM SAID SETTLER DOWNWARDLY THROUGHSAID FLOW LINE TO SAID COOLER VESSEL, COMPRISING THE STEPS OF A.ADMIXING SAID ISOPARAFFINIC HYDROCARBON AND SAID OLEFINIC HYDROCARBONSWITH LIQUID HYDROGEN FLUORIDE CATALYST IN AN ALKYLATION REACTION STEP INSAID REACTION VESSEL, B. PASSING SAID REACTION MIXTURE OF HYDROCARBONS,INCLUDING ALKYLATE, PROPANE AND ISOBUTANE, AND SAID CATALYST FROM SAIDREACTION VESSEL OVERHEAD TO SAID SETTLER, C. MAINTAINING SAID SETTLER,SAID REACTOR AND SAID ACID COOLER UNDER SUFFICIENT BACK PRESSURE TOMAINTAIN ALL OF SAID REACTION MIXTURE IN LIQUID PHASE, D. WITHDRAWINGOVERHEAD FROM SAID SETTLER A HYDROCARBON PHASE WHICH COMPRISES PRIMARILYISOBUTANE AND ALKYLATE AND A MINOR AMOUNT OF PROPANE AND CATALYST, E.REDUCING THE PRESSURE ON SAID HYDROCARBONS, THEREBY REFRIGVAPORIZEEXCESS VOLATILE HYDROCARBONS, THEREBY REFRIGERATING SAID HYDROCARBONPHASE, F. PASSING AT LEAST A SUBSTANTIAL PORTION OF SAID REFRIGERATEDHYDROCARBON PHASE, INCLUDING BOTH LIQUID AND VAPOR WITHOUT SEPARATION,IN INDIRECT HEAT EXCHANGE WITH SAID ACID IN SAID COOLER WHEREBY TO LOWERTHE TEMPERATURE THEREOF, G. PASSING SAID HYDROCARBON PHASE, AFTER USE OFSAME AS A HEAT EXCHANGE MEDIUM IN STEP (F) TO A VAPOR-LIQUID SEPARATINGSTEP, H. THE VAPOR PHASE FROM SAID SEPARATING STEP BEING PASSED TO ADEPROPANIZING STEP AND OVERHEAD FROM SAID DEPROPANIZING STEP BEINGPASSED TO AN HF STRIPPING STEP, I. RECYCLING HYDROGEN FLUORIDE CATALYSTFROM SAID STRIPPING STEP TO THE ALKYLATION REACTION IN STEP (A), J.PASSING A FIRST PORTION OF THE SEPARATION STEP LIQUID BOTTOMS FROM STEP(G) TO A DEISOBUTANIZING STEP AND RECYCLING OVERHEAD LIQUIDS FROM SAIDDEISOBUTANIZING STEP TO THE REACTION STEP (A), AND K. WITHDRAWINGALKYLATE PRODUCT BOTTOMS FROM SAID DEISOBUTANIZING STEP.
 3. A process asin claim 1 including passing a minor portion of the said refrigeratedhydrocarbon phase in indirect heat exchanging relationship with thefeeds to the reaction step (a).
 4. A process as in claim 1 includingrecycling the depropanizing step bottoms to said vapor-liquid separatingstep (g).
 5. A process as in claim 1 including passing a second portionof the separation step liquid bottoms from step (g) as recycle feed tothe alkylation reaction step.
 6. A process as in claim 1 whereinhydrogen fluoride catalyst is recycled from the HF stripping step tosaid flow line from said settler to said acid cooler.
 7. A process as inclaim 1 wherein hydrogen fluoride catalyst is recycled from said HFstripping step to join the hydrocarbon reactant feeds to the reactionstep.
 8. A process of effluent refrigeration applied to the alkylationof isoparaffinic hydrocarbons by olefinic hydrocarbons wherein hydrogenfluoride is the alkylation reaction catalyst and the reaction vesselcomprises an elongate vertical tube interconnecting an overhead settlervessel and a below-situated acid cooler vessel, there being anadditional valve-controlled recycle flow line interconnecting the setterand acid cooler, whereby circulation of liquid alkylation reactionmixture occurs upwardly through said reaction vessel to said settler andseparated acid returns from said settler downwardly through said flowline to said cooler vessel, comprising the steps of: a. admixing saidisoparaffinic hydrocarbons and said olefinic hydrocarbons with liquidhydrogen fluoride catalyst in an alkylation reaction step in saidreaction vessel, b. passing said reaction mixture of hydrocarbons,including alkylate, propane and isobutane, and said catalyst from saidreaction vessel overhead to said settler, c. maintaining said settler,said reactor and said acid cooler under sufficient back pressure tomaintain all of said reaction mixture in liquid phase, d. withdrawingoverhead from said settler a hydrocarbon phase which comprises primarilyisobutane and alkylate and a minor amount of propane and catalyst, e.reducing the pressure on said hydrocarbon phase to vaporize excessvolatile hydrocarbons, thereby refrigerating said hydrocarbon phase, f.passing at least a substantial portion of said refrigerated hydrocarbonphase, including both liquid and vapor, without separation, in indirectheat exchange with said acid in said acid cooler, whereby to lower thetemperature thereof, g. passing said hydrocarbon phase, after use ofsame as a heat exchange medium in step (f) to a vapor-liquid separatingstep, h. a first portion of said vapor phase from said separating stepbeing passed to a depropanizing step and overhead from saiddepropanizing step being passed to an HF stripping step, i. recyclinghydrogen fluoride catalyst from said stripping step to the alkylationreaction in step (a), j. a second portion of said vapor phase separatedfrom said separating step being recycled after compression andcondensation to join the hydrocarbon reactant feeds to the reaction step(a), and k. separating an alkylate product from the liquid bottoms fromsaid separating step.
 9. A process as in claim 8 wherein the liquidbottoms from said separating step (g) are passed in their entirety to adeisobutanizing step, the overhead from the deisobutanizing step beingrecycled to the reaction step (a) and the liquid bottoms from saiddeisobutanizing step being withdrawn as alkylate product.
 10. A processof effluent refrigeration applied to the alkylation of isoparaffinichydrocarbons by olefinic hydrocarbons where hydrogen fluoride is thealkylation reaction catalyst, there being separate vessels for reactionand settling steps comprising; a. admixing said isoparaffinichyDrocarbons and said olefinic hydrocarbons with liquid hydrogenfluoride catalyst in an alkylation reaction step in said reactionvessel, b. passing said reaction mixture of hydrocarbons, includingalkylate, propane and isobutane, and said catalyst from said reactionvessel to said settler, c. maintaining said settler and said reactionvessel under sufficient back pressure to maintain all of said reactionmixture in liquid phase, d. separating hydrogen fluoride catalyst asliquid bottoms from said settling step and recycling a first portion ofsaid catalyst to the reaction step (a), e. withdrawing overhead fromsaid settler a hydrocarbon phase which comprises primarily isobutane andalkylate and a minor amount of propane and catalyst, f. reducing thepressure on said hydrocarbon phase to vaporize excess volatilehydrocarbons and thereby refrigerate said hydrocarbon phase, g. passingat least a substantial portion of said refrigerated hydrocarbon phase,including both liquid and vapor without separation, in indirect heatexchange with said reaction mixture in the reaction step (a) whereby tolower the temperature thereof, h. said refrigerated hydrocarbon phase,after being used as a heat exchange medium, being passed to a separatingstep wherein liquid and vapor phases are separated and a first portionof the liquid phase from said separating step is passed to adeisobutanizing step, i. the overhead from said deisobutanizing stepbeing recycled to the reaction step (a), the liquid bottoms from thedeisobutanizing step being withdrawn as alkylate product, j. a secondportion of said catalyst from said settling step being passed to ahydrogen fluoride regenerating step, and the regenerated hydrogenfluoride catalyst from said regenerating step is recycled to thealkylation reaction step (a), k. the vapor phase from said separatingstep being compressed, condensed and passed to a depropanizing step andoverhead from said depropanizing step being passed to an HF strippingstep, and
 11. A process as in claim 10 wherein a portion of saidrefrigerated hydrocarbon phase is passed in indirect heat exchangingrelationship with a catalyst recycle from the settling step (b) to thereaction step (a).
 12. A process as in claim 10 wherein a minor portionof said refrigerated hydrocarbon phase is passed in indirect heatexchanging relationship with the hydrocarbon reactant feeds to thereaction step (a).
 13. A process as in claim 10 wherein a minor portionof said refrigerated hydrocarbon phase is passed in indirect heatexchanging relationship with both the catalyst recycle from the settlingstep (b) and the hydrocarbon reactant feeds to the reaction step (a).